Hammer Curls ( FOR GIRTH ?? )

I was in the gym lastnight, and a friend of mine told me that by doing hammer curls, it adds girth to your biceps . (( Is this TRUE ?? )) I do both DB curls and Hammer curls, but I did not know that thats exactly what the hammer curls did , or susposedly does. You will have to excuse me if this is a newbie question...
By girth, I am talking over all thickness... Makes it wider.
Heck I honestly do not know. I just know they give me awsome forearm pumps or so it seems...

Stinger, Hammer Curls build the brachialis (the outside bicep muscle) and brachioradialis (the connector muscle between the main bicep and the forearm muscle). Wehn your brachialis muscle is really developed, it does give the appearance of a thicker, wider arm.

Thanks Viper... Thats the info I was looking for.. Needed to make sure my buddy was not blowing smoke.
(( Guess he was right )) Just kidding, he is a good guy. Just know I can check out his info here and make sure its correct.